Enter your height and weight to see your body mass index (BMI) and where it falls on the World Health Organization's adult weight categories. It works in metric (cm and kg) or imperial (feet, inches and pounds), and the result updates as you type. Everything is calculated in your browser; nothing you enter is sent anywhere.
How it works
BMI is your weight in kilograms divided by the square of your height in meters: BMI = kg ÷ m². In imperial units the calculator first converts your height (feet × 12 + inches, × 0.0254) to meters and your weight (pounds × 0.45359237) to kilograms, so both unit systems give the same result. The result is placed on the WHO adult scale: below 18.5 is underweight, 18.5 to 24.9 is a healthy (normal) weight, 25 to 29.9 is overweight and 30 or more is obesity. The colored bar shows where your value sits between 15 and 40. BMI is a quick screening number, not a diagnosis. It doesn't tell muscle from fat, so muscular athletes can score as overweight, and it can underestimate body fat in older adults who have lost muscle. It doesn't apply to children and teenagers, who are assessed with age- and sex-specific percentiles, or during pregnancy. Some health bodies use lower cut-offs for people of Asian descent. If your result worries you, talk to a doctor.
Worked example
Someone 170 cm tall weighing 70 kg: 1.70 × 1.70 = 2.89, and 70 ÷ 2.89 = 24.2, a healthy weight. The same person at 82 kg would have a BMI of 28.4 (overweight). In imperial units, 5 ft 7 in and 154 lb gives 24.1; the small difference comes from 5 ft 7 in being 170.2 cm rather than exactly 170.